1. Field of the Invention
The present invention relates to monitoring health of a vessel containing fluids, such as a pipeline carrying oil from oil fields to an oil depot. In particular, the current invention relates to monitoring health of a vessel using a sensor suite that is easily attached to an outer skin of the vessel.
2. Description of the Related Art
The past approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not to be considered prior art to the claims in this application merely due to the presence of these approaches in this background section.
Pipelines are of great commercial importance. For example, oil pipelines carry crude oil from the frozen, relatively inaccessible Arctic regions to more accessible ports where the oil is loaded onto tankers for transport to oil markets. Other pipelines carry natural gas and chemicals from remote regions to processing stations. These pipelines are constructed by welding together sections of pipe. For example, sections of pipe with diameters of about four feet and lengths of about 40 feet are welded together in the Trans-Alaskan pipeline. Economies of great industrial states depend on the reliable transport of oil and other fluid commodities, such as natural gas, slurries, and chemicals, through such pipelines.
When a failure occurs in a pipeline, large costs are incurred. For example, leaks and ruptures in an oil pipeline may lead to the spillage of hundreds of thousands to millions of gallons of crude oil into the area surrounding the region. The Trans-Siberian Oil Pipeline typically releases five percent (5%) to seven percent (7%) of its transported oil each year; in 1991 alone that amounts to about seven million (7,000,000) barrels. Recently, a corroded pipeline spilled roughly one hundred thousand (100,000) gallons of crude oil and saltwater onto the Alaskan tundra. Although a crew plugged the leak in twelve minutes, the spillage endangered the crew""s lives and polluted a large area.
Much of the spilled oil is lost into the ground leading to a cost related to the current market price for that lost oil. In addition, the spillage pollutes the environment in the area for an extended period of time, leading to short-term additional costs while that environment is unusable, and long-term costs while that environment is contaminated. Further costs are involved in cleaning up the environment to restore it to a useful or less contaminated state. Additional costs are incurred if the spillage occurs in an environmentally sensitive area because either additional clean-up is mandated by law or biodiversity is diminished by the contamination, or both. Furthermore, costs are incurred while the pipeline is shut down for repair. Natural gas or chemical leaks can be substantially more dangerous.
To reduce the costs of such failures, significant efforts are expended to monitor the health of pipelines to detect faults before they lead to rupture and spillage, or to quickly detect rupture and shut down the transport of fluid through the pipeline to reduce the spillage that does occur. Monitoring and maintenance costs for pipeline structures may exceed the original installation costs for the pipeline.
In one approach, persons patrol the pipeline and manually inspect the pipe to detect and repair faults that may lead to ruptures. This is a time consuming process, and human involvement can become expensive. A significant hindrance to this approach is the length of the pipeline and the hostile environment along great sections of this length. A pipeline may be about a thousand miles long or longer. Environmental conditions along the pipeline may be harsh and hazardous to humans. In the Arctic, during winter months, much of the pipeline""s length is in complete darkness, under many feet of snow, at temperatures well below freezing, and subjected to high winds. If a pipe does rupture, a great deal of oil may spill in the time between visits by a human inspector.
In another approach, the fluid flow is cut off through a segment of the pipeline between valves, and robots with inspection equipment pass through the empty pipe sections looking for faults. For example, robots called xe2x80x9cpigsxe2x80x9d carry video equipment that sends pictures back to a control room where they are viewed by human observers. While sufficient for many purposes, and less expensive than human inspectors, there are some deficiencies. One disadvantage is that fluid flow must be turned off while the pigs run through pipe sections in the segment. Another disadvantage is that ruptures that occur while fluid is being transported are not detected.
In another approach, instruments arc installed at various locations along the pipeline to detect faults and ruptures. However this approach is not considered practical for long pipelines for a variety of reasons.
One reason that this approach is not considered practical is that instruments require a power source, such as electrical power, and generators used for electrical power are far apart because the pipelines pass through large unpopulated areas. Power lines are not currently available along the entire length of many pipelines. Simple wires running parallel to the pipeline for power are subject to attenuation and are difficult to maintain. Batteries have short lifetimes in many of the extreme conditions that predominate along some pipelines, so they involve frequent visits for replacement. Windmills provide power only intermittently and solar panels are useless many months of the year in arctic regions.
In addition, it is difficult to install and maintain different sensors along the great length of the pipe. In many cases, the fluid flow through a segment of pipe between valves must be shut down so that sensors, such as pressure sensors, can be installed inside sections of the pipe. While the pipeline is carrying fluid it is difficult to determine whether the sensors are still in place and working. If a sensor needs repair or replacement, flow through the segment may have to be shut down for some period of time.
Furthermore it is difficult to communicate with the sensors once installed. Simple wires running parallel to the pipeline for data communication are subject to attenuation and are difficult to maintain, as are lines for power. Radio transmitters to transmit data over hundreds of miles consume considerable amounts of power that rapidly deplete batteries.
Based on the foregoing, there is a clear need for techniques to monitor the health of pipelines that do not suffer the disadvantages of the above approaches. For example, there is a need for techniques to monitor pipeline health that are automatic, inexpensive, easy to install, and do not require wires for power or communication.
Techniques are provided for monitoring health of a vessel. In one aspect of the invention, a method includes attaching a sensor suite of one or more sensors to an outer skin of the vessel and providing power for the sensor suite based on a temperature difference between a fluid temperature of a contained fluid inside the vessel and an ambient temperature outside the vessel.
According to an embodiment of this aspect, the sensor suite is connected to a transmitter to communicate data based on sensor output from the sensor suite to a receiver. Power for the transmitter is also provided based on the temperature difference.
According to another embodiment using the transmitter, multiple communication relays are provided at corresponding locations along the vessel, each relay including a receiver and a transmitter for communicating the data based on the sensor suite. Power for each communication relay is based on a temperature difference between the contained fluid inside the vessel and an ambient temperature outside the vessel in the vicinity of the communication relay.
According to another embodiment of this aspect, the sensor suite is connected to a processor to generate data based on sensor output from the sensor suite. Power is provided for the processor based on the temperature difference.
According to another embodiment of this aspect, the processor is configured to determine whether output from the sensor suite deviates by more than a threshold amount from a baseline output that is associated with normal conditions for the vessel.
According to another aspect of the invention, a method includes cinching around an outer skin of the vessel, at a weld between successive sections of the vessel, a belt that contains a sensor suite of one or more sensors. Cinching the belt causes two ends of a strain gauge in the sensor suite to become rigidly attached to the outer skin of the vessel on opposite sides of the weld.
According to another aspect of the invention, an apparatus for monitoring health of a vessel includes a belt for cinching around an outer skin of the vessel at a location along the vessel. The belt further includes multiple biting members for rigidly attaching to the outer skin of the vessel when the belt is cinched around the vessel. The belt also includes a strain gauge for measuring change in distance between two ends of the strain gauge. Each end of the two ends is rigidly attached to a different one of the biting members.
According to another aspect of the invention, an apparatus for monitoring health of a vessel includes a belt for cinching around an outer skin of the vessel at a location along the vessel. The belt includes a sensor suite of one or more sensors for measuring properties related to the health of the vessel. The apparatus includes a thermopile that generates power based on a temperature difference between a first thermocouple of the thermopile and a second thermocouple of the thermopile. The first thermocouple is connected to the belt for making thermal contact with the outer skin of the vessel. The second thermocouple is configured for exposure to an ambient temperature of an environment outside the vessel. Power generated by the thermocouple powers the sensor suite.
According to another aspect of the invention, a pipeline includes multiple pipe sections welded together. A belt is cinched around an outer skin of a pipe section at a location along the pipeline. The belt includes multiple biting members rigidly attached to the outer skin of the pipeline. The belt also includes a strain gauge for measuring change in distance between two ends of the strain gauge. Each end of the two ends is rigidly attached to a different one of the biting members.
According to another aspect of the invention, a pipeline includes multiple pipe sections welded together. A belt is cinched around an outer skin of a pipe section at a location along the pipeline. The belt includes a sensor suite of one or more sensors for measuring properties related to health of the pipeline. The pipeline also includes a thermopile that generates power based on a temperature difference between a first thermocouple of the thermopile and a second thermocouple of the thermopile. The first thermocouple is connected to the belt in thermal contact with the outer skin of the pipeline. The second thermocouple is exposed to an ambient temperature of an environment outside the pipeline. Power generated by the thermocouple powers the sensor suite.
These techniques allow automatic, stand-alone, self-powered instrument suites to be easily deployed along a pipeline. For example, in embodiments in which the instrument suites are installed at each weld as each weld is inspected according to current schedules, an entire pipeline can be instrumented at reasonable costs within a few years of inspections. These techniques also allow the instrumented pipeline to be monitored remotely which reduces manpower costs for performing manual inspections, reduces the risks of injury from performing manual inspections during hazardous weather conditions, and reduces the likelihood of undetected leaks. The reduction in the likelihood of leaks is not only a cost benefit to those transporting fluids through a pipeline and to those who must clean up the spills, but is also a benefit to the environment and the population in the areas surrounding the pipeline.